<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .a{
            width: 300px;
            height: 300px;
            background-color: #0aa3f6;
            position: relative;
            
        }
        .b{
            width: 150px;
            height: 150px;
            background-color: #4404da;
            position:absolute;
            top: 50px;
            left: 70px;
        }
    </style>
</head>
<body>
    <div class="a">
        <div class="b"></div>
    </div>
</body>
</html>